Starting with release 2.1, gnupg will automatically run gpg-agent rather
than requiring it to be run as a daemon. The “--no-use-agent” switch
was also marked deprecated, since it no longer does anything.
This commit moves the --(no-)use-agent handling until after it is known
what version of gpg is being used.
Closes#37
Signed-off-by: James McCoy <vega.james@gmail.com>